code: def test_cap_alpha(alpha_arr, alpha_limit, new_alpha_arr):
      capped = _cap_alpha(alpha_arr, alpha_limit)
      assert np.array_equal(capped, new_alpha_arr)
  
imports: import pytest
  import numpy
  from eli5.base import Explanation, TargetExplanation
  from eli5.formatters.image import format_as_image, heatmap_to_image, expand_heatmap, _validate_heatmap, _update_alpha, _cap_alpha, _overlay_heatmap
  from .utils_image import assert_pixel_by_pixel_equal
label_desc: Use image node_id 13 for calling a global function with example usage: test_cap_alpha(alpha_arr, alpha_limit, new_alpha_arr) without return types